Kelsey the book picks up right after the movie (I think two months from where the movie left off) and it mentions events from the movie throughout the book. definitely experience them in order. movie first and then the book.
Derrick I think the book is better than the movie. But you need the movie to help follow the story, since it's a direct sequel.
Amy Stacey Watch movie then read the book because the books start two months after the end of the film.